With the election 15 days away, the Democratic and Republican tickets stumped in states they desperately want or need to win the White House. McCain was in Missouri, a state that Bush won in 2000 and 2004 and where McCain finds himself in a close race against Obama, who toured Florida on Monday.

Obama will temporarily leave the campaign trail later this week to fly to Hawaii to be at the side of his ailing 85-year-old grandmother, aides said Monday night.

The Democratic nominee will cancel campaign events Thursday in Wisconsin and Iowa, move up a rally in Indianapolis for Thursday in their place and then depart for Hawaii, said senior adviser Robert Gibbs. Gibbs declined to discuss details of Madelyn Dunham's illness, but she'd been hospitalized and released late last week and that Obama felt he could not wait until after the Nov. 4 election. He plans to spend Friday at her side and return to the campaign trail Saturday.

At rallies in St. Charles and in Belton, Mo., McCain seized on remarks that Democratic vice-presidential candidate Joe Biden had made predicting that Obama will be tested by an international crisis within his first six months in office and supporters will have to stand behind him.

"Mark my words," Biden said Sunday at the second of two fundraisers in Seattle. "It will not be six months before the world tests Barack Obama like they did John Kennedy. The world is looking. We're about to elect a brilliant 47-year-old senator president of the United States of America. . . . Watch, we're gonna have an international crisis, a generated crisis, to test the mettle of this guy."

McCain said the next president wouldn't have time to adjust to being president and that he, not Obama, had the experience to handle a crisis right away.

"We don't want a president who invites testing from the world at a time when our economy is in crisis and Americans are already fighting in two wars," McCain said. "What is more troubling is that Senator Biden told their campaign donors that when that crisis hits, they would have to stand with them because it wouldn't be apparent that Senator Obama would have the right response."

"With our nation facing two wars and 21st-century threats abroad, Senator Biden referenced the simple fact that history shows presidents face challenges from day one," Obama-Biden campaign spokesman David Wade said. "After eight years of a failed foreign policy, we need Barack Obama's good judgment and steady leadership, not the erratic and ideological Bush-McCain approach that has set back our security and standing in the world."

While McCain went after Obama on foreign policy, his running mate, Sarah Palin, hammered the Illinois senator on domestic policy. The Republican governor from Alaska continued the campaign's strategy of suggesting that Obama's tax policies are akin to socialism.

She reminded a crowd in Colorado Springs, Colo., that Obama told Joe the Plumber that he wants to "spread the wealth" through his tax plan.

"Barack Obama calls it 'spreading the wealth.' Joe Biden calls it 'patriotic,' " Palin said. "But Joe the Plumber said it sounded to him like socialism . . . and now is no time to experiment with that."

Obama, for his part, told a rally in Florida that now isn't the time to experiment with a McCain home-mortgage bailout plan that calls for using money from the recently passed $700 billion bailout package and $300 billion from a Federal Housing Authority fund that Congress passed in July to direct the Treasury secretary to buy troubled mortgage loans in order to help families stave off foreclosure.

Under the plan, homeowners would be allowed to stay in their homes and get more affordable government-backed loans.

"His plan would amount to a $300 billion bailout for Wall Street banks," Obama said. "And guess what? It would all be paid for by you, the American taxpayer. That might sound like a good idea to the former bank lobbyists running my opponent's campaign. But that's not the change America needs."

As early voting began Monday in Florida, Obama kicked off two days of campaigning in the state, appearing in Orlando alongside his former primary rival, New York Sen. Hillary Clinton. On Tuesday, he was to campaign in more Democratic South Florida.

"We cannot falter, we cannot stop, we cannot take a single vote for granted," Hillary Clinton told a crowd estimated at 20,000 gathered in a staging area outside the Amway Arena in Orlando and an estimated 30,0000 who spilled onto area streets.

Clinton and Obama had taken the stage arm in arm. She asked the audience to go to their friends and neighbors and urge them to vote for him. "Tell them Hillary sent you," she said. "Now is the time to close the deal for Barack Obama."

Clinton thanked her primary supporters. "Now I'm asking you to work as hard for Barack as you worked for me," she said. "This is the mad dash to the finish line. Florida is a battleground and Central Florida is the battleground of the battleground and we need your help."

Earlier in Tampa, several members of the World Series-bound Rays baseball team introduced Obama.

"Florida, it's time for a change," Obama told the audience of 8,000 at Steinbrenner Field. "You know it, I know it and the American people know it."

The financial crisis is hitting Florida hard, with foreclosures high and retiree savings eroding. Where Florida once seemed to favor McCain, polls now show Obama slightly ahead. Democratic Sen. Bill Nelson, who warmed up the audience by warning that the Arizona senator would reduce Social Security benefits and spending for NASA, said Floridians' fiscal woes had been "huge" in terms of shifting momentum to Obama.

"I really think he's going to win Florida," Nelson said.

Obama told the crowd in Tampa that foreclosures were up 30 percent in Florida in the last year. He said that Florida's 115,000 jobs lost this year were more than in any other state.

Alluding to Joe the Plumber, Obama said that under his tax plans, almost all working Americans would see their taxes cut, and that includes, "I'm pretty sure, 99.9 percent of plumbers."

Obama said that McCain was "out of ideas, out of touch and running out of time."